General devices and methods for measuring the electrical activities of the heart of living beings, particularly of humans, are known.
For measuring the heart activity so-called electrocardiographs are known which measure electrical potentials in the heart muscle on the skin surface by using single electrodes attached to the subject to be examined.
The electrodes can be attached to or placed on points of the body in various configurations in order to measure, i.e., derive the respective potentials at each point. Various lead systems exist, using not only varying numbers of electrodes but also varying points on the body to derive each individual signal. The potentials are generally measured between two specified electrodes. The measured potential in time forms the so-called electrocardiogram.
In principle a physician or an automatic analyzing algorithm needs to know the arrangement of the electrodes, and between which electrodes the individual potentials are measured in order to be able to interpret an electrocardiogram in a meaningful way.
As shown, for example, in prior art DE 100 65 578 A1 it frequently occurs in practice that the electrodes are not attached exactly in the position specified for the lead system, and that, in addition, the electrodes are interchanged. The method disclosed there uses a lead system working with 10 electrodes, and is able to recognize interchanged or incorrectly positioned electrodes by means of a vector analysis or vectorcardiography. This vector analysis is based on assigning a vector to each electrode and comparing the result of the vector analysis with a reference result. In case of an adequate deviation the system recognizes that electrodes have been interchanged.
Furthermore, conversion of different lead systems to each other is known, using, for example, vectorcardiography. For example, U.S. Pat. No. 4,850,370 discloses a lead system using only 4 electrodes to convert into a 10- or 12-channel electrocardiogram.
As mentioned above, placing of the electrodes and, in particular, the correct assignment, i.e. the correct “permutation” of electrodes are prone to errors. Even trained personnel frequently chose an incorrect electrode permutation, even when electrodes and associated signal inputs of an electrocardiograph are color coded.
Due to an increasing number of cardiovascular diseases, apart from inpatient or outpatient monitoring of patients, long term ECG monitoring is often required where the patients carry a portable ECG device. Furthermore, it is useful for heart patients to be able to perform an ECG reading, if needed, without the presence of medical professionals, for example in the case of so-called home monitoring. The risk of an untrained user interchanging the electrodes when attaching them to himself/herself—particularly when under stress—is significantly higher than with medical professionals. However, the untrained user would need a system that if needed or in an emergency, generate an ECG and reliably output the results, for example a warning that he/she should immediately get emergency medical care.
Another known way of avoiding permutations of the electrodes is a fixed arrangement of the electrodes by securing them to, for example, a vest, a belt, a harness or other mechanical means. However, such solutions are often inflexible because they cannot easily adapted to different body sizes or various anatomical circumstances. Furthermore, such systems are often uncomfortable to wear.
The objective of the present invention is to provide an improved device and an improved method for recording an electrocardiogram.